0001564590-21-024523 | 10-Q | XBRL Viewer

Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2021	Apr. 30, 2021
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	--12-31
Entity Registrant Name	Dyne Therapeutics, Inc.
Entity Central Index Key	0001818794
Entity File Number	001-39509
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	36-4883909
Entity Address, Address Line One	830 Winter Street
Entity Address, City or Town	Waltham
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02451
City Area Code	781
Local Phone Number	786-8230
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Common Stock, Shares Outstanding		51,205,932
Entity Shell Company	true
Document Quarterly Report	true
Document Transition Report	false
Title of 12(b) Security	Common Stock, $0.0001 par value per share
Trading Symbol	DYN
Security Exchange Name	NASDAQ

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 310,949	$ 300,852
Marketable securities	172,136	44,462
Prepaid expenses and other current assets	3,983	3,773
Total current assets	487,068	349,087
Property and equipment, net	1,777	1,946
Right-of-use asset	562
Restricted cash and other assets	2,303	2,301
Total assets	491,710	353,334
Current liabilities:
Accounts payable	5,760	3,440
Accrued expenses and other current liabilities	7,094	7,527
Lease liability	596
Total liabilities	13,450	10,967
Commitments and contingencies (Note 9)
Stockholders’ equity
Preferred stock
Common stock, $0.0001 par value; 200,000,000 shares authorized at March 31, 2021 and December 31, 2020; 51,458,066 and 45,446,903 shares issued and 51,158,276 and 45,076,574 shares outstanding at March 31, 2021 and December 31, 2020, respectively	6	5
Additional paid-in capital	582,473	421,572
Accumulated other comprehensive loss	(68)	(27)
Accumulated deficit	(104,151)	(79,183)
Total stockholders’ equity	478,260	342,367
Total liabilities and stockholders’ equity	$ 491,710	$ 353,334

Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating expenses:
Research and development	$ 18,625	$ 6,089
General and administrative	6,509	1,764
Total operating expenses	25,134	7,853
Loss from operations	(25,134)	(7,853)
Other (expense) income:
Interest income	166	24
Interest expense		(57)
Total other (expense) income, net	166	(33)
Net loss	$ (24,968)	$ (7,886)
Net loss per share—basic and diluted	$ (0.50)	$ (0.90)
Weighted-average common shares outstanding used in net loss per share—basic and diluted	49,472,497	8,756,513
Comprehensive loss:
Net loss	$ (24,968)	$ (7,886)
Other comprehensive loss:
Unrealized (losses) gains on marketable securities, net	(41)
Comprehensive loss	$ (25,009)	$ (7,886)

Condensed Consolidated Statements of Stockholders' Equity (Deficit) (Unaudited) - USD ($) $ in Thousands	Total	Series A Convertible Preferred Stock	Convertible Preferred Stock	Convertible Preferred Stock Series A Convertible Preferred Stock	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit
Beginning Balance at Dec. 31, 2019	$ 14,036		$ 27,429		$ 1	$ 6,352		$ (19,746)
Beginning Balance, Shares at Dec. 31, 2019			32,500,000		2,586,535
Issuance of stock, net of issuance costs		$ 1,972		$ 1,972
Issuance of stock, net of issuance costs, Shares				2,000,000
Stock-based compensation	66					66
Vesting of restricted shares					70,538
Net loss	(7,886)							(7,886)
Ending Balance at Mar. 31, 2020	8,188		$ 29,401		$ 1	6,418		(27,632)
Ending Balance, Shares at Mar. 31, 2020			34,500,000		2,657,073
Beginning Balance at Dec. 31, 2020	342,367				$ 5	421,572	$ (27)	(79,183)
Beginning Balance, Shares at Dec. 31, 2020					45,076,574
Issuance of stock, net of issuance costs	157,237				$ 1	157,236
Issuance of stock, net of issuance costs, Shares					6,000,000
Exercise of stock options	$ 13					13
Exercise of stock options, Shares	11,163				11,163
Stock-based compensation	$ 3,652					3,652
Vesting of restricted shares					70,539
Unrealized (losses) gains on marketable securities, net	(41)						(41)
Net loss	(24,968)							(24,968)
Ending Balance at Mar. 31, 2021	$ 478,260				$ 6	$ 582,473	$ (68)	$ (104,151)
Ending Balance, Shares at Mar. 31, 2021					51,158,276

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash flows from operating activities:
Net loss	$ (24,968)	$ (7,886)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	3,652	66
Depreciation and amortization expense	238	150
Amortization of debt discount		12
Non-cash lease expense	(7)	(2)
Amortization (accretion) of premium (discount) on marketable securities	492
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	331	(129)
Accounts payable and other liabilities	1,869	501
Net cash used in operating activities	(18,393)	(7,288)
Cash flows from investing activities:
Purchases of property and equipment	(9)	(211)
Purchases of marketable securities	(132,186)
Maturities of marketable securities	3,820
Net cash used in investing activities	(128,375)	(211)
Cash flows from financing activities:
Proceeds from follow-on public offering of common stock, net of issuance costs	157,237
Proceeds from issuance of debt, net of issuance costs		9,936
Proceeds from issuance of convertible preferred stock, net of issuance costs		1,972
Proceeds from exercise of stock options	13
Net cash provided by financing activities	157,250	11,908
Net increase in cash and cash equivalents	10,482	4,409
Cash, cash equivalents and restricted cash, beginning of period	303,153	14,632
Cash, cash equivalents and restricted cash, end of period	313,635	19,041
Supplemental cash flow information:
Cash paid for interest and taxes		14
Supplemental disclosure of non-cash investing and financing information:
Purchase of property and equipment in accounts payable	$ 59	8
Issuance costs from convertible preferred stock included in accounts payable or accrued expenses		$ 18

Nature of the Business and Basis of Presentation

3 Months Ended

Mar. 31, 2021

Accounting Policies [Abstract]

Nature of the Business and Basis of Presentation

1. Nature of the Business and Basis of Presentation

Dyne Therapeutics, Inc. (the “Company”) is building a leading muscle disease company focused on advancing innovative life-transforming therapeutics for people living with genetically driven diseases that was incorporated in Delaware on December 1, 2017 and has a principal place of business in Waltham, Massachusetts.

The Company is subject to risks and uncertainties common to early-stage companies in the biotechnology industry, including, but not limited to, development by competitors of new technological innovations, dependence on key personnel, protection of proprietary technology, risks of failure of preclinical studies and clinical trials, the need to obtain marketing approval for its product candidates, fluctuations in operating results, compliance with government regulations, the ability to establish clinical- and commercial-scale manufacturing processes, the impact of the COVID-19 pandemic and the ability to secure additional capital to fund operations. Programs currently under development will require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approval prior to commercialization of a product. These efforts require significant amounts of additional capital, adequate personnel and infrastructure and extensive compliance-reporting capabilities. Even if the Company’s development efforts are successful, it is uncertain when, if ever, the Company will realize significant revenue from product sales.

On September 21, 2020, the Company completed its initial public offering (“IPO”) pursuant to which it issued and sold 14,089,314 shares of its common stock, including 1,837,736 shares pursuant to the full exercise of the underwriters’ option to purchase additional shares, at a public offering price of $19.00 per share, resulting in net proceeds of $246.4 million, after deducting underwriting discounts and commissions and offering expenses. Upon the closing of the IPO, all of the Company’s then outstanding convertible preferred stock automatically converted into shares of common stock.

On January 25, 2021, the Company completed a follow-on public offering of common stock pursuant to which it issued and sold 6,000,000 shares of its common stock at a public offering price of $28.00 per share, resulting in net proceeds of $157.2 million, after deducting underwriting discounts and commissions and offering expenses.

The accompanying condensed consolidated financial statements have been prepared on the basis of continuity of operations, realization of assets and the satisfaction of liabilities and commitments in the ordinary course of business. Since inception, the Company has funded its operations with proceeds from the sales of preferred stock and common stock, including the IPO completed in September 2020 and the follow-on offering completed in January 2021. The Company expects to continue to generate operating losses for the foreseeable future. The Company expects that its cash, cash equivalents and marketable securities will be sufficient to fund its operating expenses and capital expenditure requirements for at least 12 months from the issuance of these condensed consolidated financial statements.

To continue its development efforts, the Company will need to obtain substantial additional funding through public or private equity offerings, debt financings, collaborations, strategic alliances and/or licensing arrangements in order to fund its research and development and ongoing operating expenses. The Company may not be able to obtain financing on acceptable terms, when needed or at all, and the Company may not be able to enter into collaborations, strategic alliances or licensing arrangements. The terms of any financing may adversely affect the holdings or the rights of the Company’s stockholders. Any collaborations, strategic alliances or licensing arrangements may require the Company to relinquish rights to certain of its technologies, future revenue streams, research programs or product candidates or grant licenses on terms that may not be favorable to the Company. If the Company is unable to obtain funding, the Company could be forced to delay, limit, reduce or eliminate some or all of its research and development programs, pipeline expansion or future commercialization efforts or grant rights to develop and market product candidates, which could adversely affect its business prospects. Although management will continue to pursue these plans, there is no assurance that the Company will be successful in obtaining sufficient funding on terms acceptable to the Company to fund continuing operations when needed or at all.

To date, the Company has not experienced material business disruptions, including with its vendors, as a result of the COVID-19 pandemic. In March 2020, the Company implemented a remote working policy for many of its employees and began restricting non-essential travel, and in May 2020, when Massachusetts began its staged reopening plan, the Company began implementing a return-to-work plan, in accordance with the guidance and requirements of federal and state authorities. The Company expects to continue to take actions as may be required or recommended by government authorities or as it determines are in the best interests of its employees and other business partners. The Company is continuing to monitor the potential impact of the pandemic, but cannot be certain what the overall impact will be on its business, financial condition, results of operations and prospects.

Summary of Significant Accounting Policies

3 Months Ended

Mar. 31, 2021

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

The accompanying financial statements have been prepared in conformity with generally accepted accounting principles (“GAAP”) in the United States of America. Any reference in these notes to applicable guidance is meant to refer to the authoritative GAAP as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Update (“ASU”) of the Financial Accounting Standards Board (“FASB”).

The financial statements of the Company included herein have been prepared, without audit, pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). The unaudited interim financial statements have been prepared on the same basis as audited annual financial statements, except certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted from this report, as is permitted by such rules and regulations. In the opinion of management, the interim financial information reflects all adjustments, all of which are of a normal and recurring nature, necessary for a fair representation of the results for the reported periods. Accordingly, these financial statements should be read in conjunction with the financial statements and notes thereto included in the Company’s annual report on Form 10-K filed with the SEC on March 4, 2021. The results for the three months ended March 31, 2021 are not necessarily indicative of results to be expected for the year ending December 31, 2021, any other interim periods, or any future year or period.

Marketable securities

The Company’s marketable securities as of March 31, 2021 consisted of commercial paper, certificates of deposit, corporate debt securities and US treasury securities and are classified as available-for-sale and are reported at fair value. Unrealized losses on available-for-sale debt securities are reported as a component of accumulated other comprehensive loss in stockholders’ equity. Realized gains and losses are based on the specific identification method and are included as a component of other income (expense), net in the condensed consolidated statements of operations and comprehensive loss.

The Company evaluates its marketable securities with unrealized losses for other-than-temporary impairment. When assessing marketable securities for other-than-temporary declines in value, the Company considers such factors as, among other things, how significant the decline in value is as a percentage of the original cost, how long the market value of the investment has been less than its original cost, the Company’s ability and intent to retain the investment for a period of time sufficient to allow for any anticipated recovery in fair value and market conditions in general. If any adjustment to fair value reflects a decline in the value of the investment that the Company considers to be “other than temporary,” the Company reduces the investment to fair value through a charge to the statement of operations and comprehensive loss. No such adjustments were necessary during the periods presented.

Property and equipment

Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation and amortization expense is recognized using the straight-line method over the estimated useful life of each asset as follows:

		Estimated Useful Life
Laboratory equipment		5 years
Furniture and fixtures		5 years
Computer equipment		3 years
Leasehold improvements		Shorter of life of lease or 10 years

Costs for capital assets not yet placed into service are capitalized as construction-in-progress and depreciated once placed into service. Upon retirement or sale, the cost of assets disposed of and the related accumulated depreciation and amortization are removed from the accounts and any resulting gain or loss is included in loss from operations. Expenditures for repairs and maintenance which do not improve or extend the life of the respective assets are charged to expense as incurred.

Leases

Prior to January 1, 2021, the Company accounted for leases under ASC 840, Leases (“ASC 840”). The Company recorded monthly rent expense on a straight-line basis, equal to the total of the payments due over the lease term, divided by the number of months of the lease term. The difference between rent expense recorded and the amount paid was charged to deferred rent.

Effective January 1, 2021, the Company adopted ASU 2016-02, Leases (Topic 842) (“ASC 842”), using the modified retrospective approach transition method as of the date of adoption. Under this method, financial statements for reporting periods after adoption are presented in accordance with ASC 842 and prior-period financial statements continue to be presented in accordance with ASC 840. Upon adoption, the Company recognized lease liabilities totaling $0.8 million and right-of-use assets totaling $0.7 million.

Under ASC 842, at the inception of an arrangement, the Company determines whether the arrangement is or contains a lease based on the unique facts and circumstances presented in the arrangement, including whether the Company controls the use of identified assets. The Company classifies leases with a term greater than one year as either operating or finance leases at the lease commencement date and records a right-of-use assets and current and non-current lease liabilities, as applicable on the balance sheet. The Company has elected not to recognize on the balance sheet leases with terms of one year or less, but payments are recognized as expense on a straight-line basis over the lease term. If a lease includes options to extend the lease term, the Company does not assume the option will be exercised in its initial lease term assessment unless there is reasonable certainty that the Company will renew based on an assessment of economic factors present as of the lease commencement date. The Company monitors its plans to renew its material leases each reporting period.

Lease liabilities and the corresponding right-of-use assets are recorded based on the present value of lease payments over the remaining lease term. The present value of future lease payments are discounted using the interest rate implicit in lease contracts if that rate is readily determinable; otherwise the Company utilizes its incremental borrowing rate (“IBR”), which reflects the fixed rate at which the Company could borrow on a collateralized basis over a similar term, the amount of the lease payments in a similar economic environment. After lease commencement and the establishment of a right-to-use asset and operating lease liability, lease expense is recorded on a straight-line basis over the lease term.

The Company enters into contracts that contain both lease and non-lease components. Non-lease components include costs that do not provide a right-to-use a leased asset but instead provide a service, such as maintenance costs. The Company has elected to account for the lease and non-lease components together as a single component for all classes of underlying assets. Variable costs associated with the lease, such as maintenance and utilities, are not included in the measurement of right-to-use assets and lease liabilities but rather are expensed when the events determining the amount of variable consideration to be paid have occurred.

Segment information

Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision maker, or decision-making group, in making decisions on how to allocate resources and assess performance. The Company’s chief operating decision maker is the chief executive officer (“CEO”). The CEO views the Company’s operations and manages the business as one operating segment.

Fair value measurements

Certain assets and liabilities are carried at fair value. Fair value is defined as the amount that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable:

•	Level 1—Unadjusted quoted prices in active markets that are accessible to the reporting entity at the measurement date for identical assets and liabilities.

•	Level 2—Inputs other than quoted prices in active markets for identical assets and liabilities that are observable either directly or indirectly for substantially the full term of the asset or liability. Level 2 inputs include the following:

•

quoted prices for similar assets and liabilities in active markets;

•

quoted prices for identical or similar assets or liabilities in markets that are not active;

•

observable inputs other than quoted prices that are used in the valuation of the asset or liabilities (e.g., interest rate and yield curve quotes at commonly quoted intervals); and

•

inputs that are derived principally from or corroborated by observable market data by correlation or other means.

•	Level 3—Unobservable inputs for the assets or liability (i.e., supported by little or no market activity). Level 3 inputs include management’s own assumptions about the assumptions that market participants would use in pricing the asset or liability (including assumptions about risk).

Net loss per share

In the periods prior to the IPO, the Company followed the two-class method when computing net loss per share as the Company had issued shares that met the definition of participating securities. The two-class method determines net income (loss) per share for each class of common and participating securities according to dividends declared or accumulated and participation rights in undistributed earnings. The two-class method requires income available to common stockholders for the period to be allocated between common and participating securities based upon their respective rights to receive dividends as if all income for the period had been distributed. During periods of loss, the Company does not allocate loss to participating securities because they have no contractual obligation to share in the losses of the Company. Following the IPO, there were no participating securities outstanding.

Basic net loss per share is computed by dividing the net loss by the weighted average number of shares of common stock outstanding for the period. Diluted net loss is computed by adjusting net loss to reallocate undistributed earnings based on the potential impact of dilutive securities. Diluted net loss per share is computed by dividing the diluted net loss by the weighted average number of shares of common stock outstanding for the period, including potential dilutive common shares assuming the dilutive effect of common stock equivalents.

Fair Value Measurements

3 Months Ended

Mar. 31, 2021

Fair Value Disclosures [Abstract]

Fair Value Measurements

4. Fair Value Measurements

The following tables set forth by security type, marketable securities for the periods presented:

	As of March 31, 2021
(in thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses			Total
Commercial paper	$	20,882	$	4	$	—		$	20,886
Certificates of deposit		119,450		3		(78	)		119,375
Corporate debt securities		11,957		1		—			11,958
US treasury notes		19,915		2		—			19,917
Total	$	172,204	$	10	$	(78	)	$	172,136

	As of December 31, 2020
(in thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses			Total
Commercial paper	$	6,412	$	—	$	—		$	6,412
Certificates of deposit		1,504		—		—			1,504
Corporate debt securities		36,573		—		(27	)		36,546
Total	$	44,489	$	—	$	(27	)	$	44,462

The following tables set forth by level, within the fair value hierarchy, the assets carried at fair value on a recurring basis for the periods presented:

	Fair value measurements as of March 31, 2021
(in thousands)	Level 1		Level 2		Level 3		Total
Assets:
Cash equivalents
Money market funds	$	185,544	$	-	$	-	$	185,544
Commercial paper		4,250		—		—		4,250
Marketable securities
Commercial paper		20,886		—		—		20,886
Certificates of deposit		—		11,958		—		11,958
Corporate debt securities		—		119,375		—		119,375
US treasury notes		19,917		—		—		19,917
Total	$	230,597	$	131,333	$	—	$	361,930

	Fair Value Measurements as of December 31, 2020
(in thousands)	Level 1		Level 2		Level 3		Total
Assets:
Cash equivalents
Money market funds	$	155,017	$	—	$	—	$	155,017
Commercial paper		2,999		—		—		2,999
Certificates of deposit		—		5,309		—		5,309
Marketable securities
Commercial paper		6,412		—		—		6,412
Certificates of deposit		—		1,504		—		1,504
Corporate debt securities		—		36,545		—		36,545
Total	$	164,428	$	43,358	$	—	$	207,786

The fair value of money market funds, commercial paper and US treasury notes were determined by the Company based on quoted market prices, which represent a Level 1 measurement within the fair value hierarchy. Certificates of deposit and corporate debt securities notes were valued by the Company using quoted prices in active markets for similar securities, which represent a Level 2 measurement within the fair value hierarchy.

There were no transfers between Level 1, Level 2, or Level 3 during the periods presented.

The following table summarizes the scheduled maturity for the Company’s marketable securities at March 31, 2021:

(in thousands)	March 31, 2021
Maturing in one year or less	$	119,510
Maturing in one year through two years		52,626
Maturing after two years		—
Total	$	172,136

Financial instruments not recorded at fair value

The carrying values of cash, accounts payable and accrued expenses that are reported on the balance sheets approximate their fair value due to the short-term nature of these assets and liabilities.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Stock-Based Awards

3 Months Ended

Mar. 31, 2021

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Awards

7. Stock-Based Awards

2018 Stock Incentive Plan

The Company’s 2018 Stock Incentive Plan (the “2018 Plan”) provided for the Company to sell or issue incentive stock options or nonqualified stock options, restricted stock, and other equity awards to employees, directors and consultants of the Company. The 2018 Plan was administered by the board of directors or, at the discretion of the board of directors, by a committee of the board of directors. The exercise prices, vesting and other restrictions were determined at the discretion of the board of directors.

The total number of shares of common stock authorized under the 2018 Plan was 8,267,252 shares. Upon the effectiveness of the 2020 Stock Incentive Plan (the “2020 Plan”), the Company ceased granting awards under the 2018 Plan, and the 1,928,487 shares of common stock remaining under the 2018 Plan became available for future issuance under the 2020 Plan.

2020 Stock Incentive Plan

In August 2020 the Company’s board of directors adopted and the Company’s stockholders approved the 2020 Plan, which became effective on September 16, 2020. The 2020 Plan provides for the grant of incentive stock options, nonstatutory stock options, stock appreciation rights, restricted stock awards, restricted stock units and other stock-based awards to employees, directors, consultants and advisors of the Company. The 2020 Plan is administered by the Company’s board of directors or by a committee appointed by the board of directors. Upon the effectiveness of the 2020 Plan, the Company ceased granting awards under the 2018 Plan. The number of shares initially reserved for issuance under the 2020 Plan was 4,884,233. The number of shares of common stock reserved for issuance under the 2020 Plan will automatically increase on the first day of each fiscal year, beginning with the fiscal year commencing on January 1, 2021 and continuing for each fiscal year until, and including the fiscal year commencing on, January 1, 2030, in an amount equal to the lower of (1) 5% of the shares of common stock outstanding on such date and (2) an amount determined by the Company’s board of directors. On January 1, 2021, 2,272,345 shares were added to the shares reserved for issuance under the 2020 Plan in the first of these annual increases.

As of March 31, 2021, 5,062,689 shares remain available for future issuance under the 2020 Plan.

2020 Employee Stock Purchase Plan

In August 2020 the Company’s board of directors adopted and the Company’s stockholders approved the 2020 Employee Stock Purchase Plan (the “2020 ESPP”), which became effective September 16, 2020. The 2020 ESPP is administered by the Company’s board of directors or by a committee appointed by the board of directors. The 2020 ESPP initially provides participating employees with the opportunity to purchase up to an aggregate of 488,414 shares of common stock. The number of shares of common stock reserved for issuance under the 2020 ESPP will automatically increase on the first day of each fiscal year, beginning with the fiscal year commencing on January 1, 2021 and continuing for each fiscal year until, and including the fiscal year commencing on, January 1, 2030, in an amount equal to the lowest of (1) 1,953,656 shares of common stock, (2) 1% of the shares of common stock outstanding on such date, and (3) an amount determined by the board of directors. As of March 31, 2021, no offering periods have commenced under the 2020 ESPP and 488,414 shares remain available for issuance.

Stock option valuation

The Company typically grants stock options at exercise prices deemed by the Board to be equal to the fair value of the common stock at the time of grant. In the periods prior to the IPO, the fair value of the common stock was determined by the Board at each measurement date based on a variety of different factors, including the results obtained from independent third-party appraisals, the Company’s financial position and historical financial performance, the status of development of the Company’s programs, the current climate in the marketplace, the illiquid nature of the common stock, the effect of the rights and preferences of the preferred stockholders, and the prospects of a liquidity event, among others. In the periods following the IPO, the fair value is determined based upon the quoted price of the Company’s common stock on Nasdaq.

The fair value of stock option grants is estimated using the Black-Scholes option-pricing model. The Company historically has been a private company and lacks company-specific historical and implied volatility information. Therefore, it estimates its expected stock volatility based on the historical volatility of a publicly traded set of peer companies and expects to continue to do so until such time as it has adequate historical data regarding the volatility of its own traded stock price. For options with service-based vesting conditions, the expected term of the Company’s stock options has been determined utilizing the “simplified” method for awards that qualify as “plain-vanilla” options. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. Expected dividend yield is based on the fact that the Company has never paid cash dividends and does not expect to pay any cash dividends in the foreseeable future.

The assumptions that the Company used to determine the grant-date fair value of options granted were as follows:

	Three Months Ended March 31,
	2021		2020
Expected volatility	74%		75%
Risk-free interest rate	0.88% — 1.13%		0.79% — 1.67%
Expected term (in years)		6		6
Expected dividend yield		—		—

Stock option activity

A summary of the Company’s stock option activity and related information for the three months ended March 31, 2021 is as follows:

(in thousands, except share and per share data)	Options			Weighted Average Exercise Price		Weighted Average Remaining Life (in years)		Aggregate Intrinsic Value
Outstanding as of January 1, 2021		6,421,589		$	6.97		9.5	$	90,112
Granted		361,000			17.70
Exercised		(11,163	)		1.20
Canceled		—			—
Outstanding as of March 31, 2021		6,771,426		$	7.55		9.3	$	59,244
Options exercisable as of March 31, 2021		822,408		$	5.34		9.0	$	8,810
Options vested or expected to vest as of March 31, 2021		6,771,426		$	7.55		9.3	$	59,244

The weighted-average grant date fair value of the options granted during the three months ended March 31, 2021 and 2020 was $11.44 and $0.68 per share, respectively. As of March 31, 2021 there was $21.8 million of unrecognized compensation expense, which the Company expects to recognize over a weighted-average period of 2.6 years. Additionally, as of March 31, 2021, the Company has unrecognized compensation cost related to unvested stock-based awards with performance-based vesting conditions for which performance has not been deemed probable of $2.6 million.

Restricted stock units

A restricted stock unit (“RSU”) represents the right to receive one share of common stock upon vesting of the RSU. The Company grants RSUs with service conditions that vest in four equal annual installments provided that the employee remains employed with the Company. The Company also grants RSUs with performance-based vesting conditions for which performance was not deemed probable at March 31, 2021. The fair value of each RSU is based on the closing price of the Company’s common stock on the date of grant. A summary of the Company’s RSU activity and related information for the 2020 Plan for the three months ended March 31, 2021:

	Number of Shares Underlying RSUs		Weighted Average Grant Date Fair Value
Issued and unvested as of January 1, 2021		403,355	$	23.60
Granted		85,900		17.67
Vested		—
Forfeited		—
Issued and unvested as of March 31, 2021		489,255	$	22.62

As of March 31, 2021, there was $8.3 million of unrecognized compensation costs related to unvested RSUs, which are expected to be recognized over a weighted-average period of 2.8 years.

Restricted common stock

During the year ended December 31, 2018, the Company granted restricted common stock with service-based vesting conditions. Shares of unvested restricted common stock may not be sold or transferred by the holder. These restrictions lapse according to the time-based vesting conditions of each award. The aggregate grant date fair value of these awards was immaterial. The following table summarizes the Company’s restricted common stock award activity for the three months ended March 31, 2021:

	Number of Restricted Shares
Issued and unvested as of January 1, 2021		370,329
Vested		(70,539	)
Issued and unvested as of March 31, 2021		299,790

The Company recorded stock-based compensation expense in the following expense categories of its statements of operations:

	Three Months Ended March 31,
(in thousands)	2021		2020
Research and development	$	1,571	$	25
General and administrative		2,081		41
Total	$	3,652	$	66

Net Loss Per Share

3 Months Ended

Mar. 31, 2021

Earnings Per Share [Abstract]

Net Loss per Share

8. Net Loss per Share

Basic and diluted net loss per share was calculated as follows:

	Three Months Ended March 31,
(in thousands, except share and per share data)	2021			2020
Numerator:
Net loss	$	(24,968	)	$	(7,886	)
Denominator:
Weighted-average common shares outstanding used in net loss per share—basic and diluted		49,472,497			8,756,513
Net loss per share—basic and diluted	$	(0.50	)	$	(0.90	)

The following potentially dilutive common stock equivalents, presented based on amounts outstanding at each period end, were excluded from the computation of diluted net loss per share for the periods indicated because including them would have had an anti-dilutive effect:

	March 31,
	2021		2020
Options to purchase common stock		6,771,426		1,498,222
Unvested restricted common stock		299,790		581,944
Unvested restricted stock units		489,255		—
Convertible preferred stock (as converted to common stock)		—		10,401,270
Total		7,560,471		12,481,436

Commitments and Contingencies

3 Months Ended

Mar. 31, 2021

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

9. Commitments and Contingencies

Operating leases

In May 2019, the Company entered into a sublease agreement for laboratory and office space in Waltham, Massachusetts. The term of the sublease commenced on July 1, 2019 and expires on December 31, 2021.

In December 2020, the Company entered into a lease agreement, which was amended in January 2021 and March 2021 (the “Lease”), pursuant to which the Company has agreed to lease approximately 68,187 square feet of additional office and laboratory space located in Waltham, Massachusetts (the “Premises”). The Lease will have a term of eight years and seven months that will commence when the Premises are ready for occupancy. The Company’s obligation for the payment of base rent for the Premises begins seven months after the commencement date and will be $0.4 million per month, increasing up to $0.5 million during the term of the Lease. The Company has two options to extend the term of the Lease, each for a period of an additional five years. The term of this lease will commence on the earlier of the date the Company commences its business operations on the Premises or the date the agreed upon improvements to the Premises are substantially completed and necessary occupancy permits are obtained. The Company expects the Premises to be ready for occupancy in the second half of 2021.

Rent expense for the three months ended March 31, 2021 and 2020 totaled $0.2 million and $0.2 million, respectively.

Summary of lease costs

The Company does not have any material finance leases as of March 31, 2021.

The components of lease cost under ASC 842 for the sublease were as follows:

(in thousands)	Three Months Ended March 31, 2021
Operating lease cost	$	190
Short term lease cost		—
Variable lease cost		114
Total lease cost	$	304

Supplemental disclosure of cash flow information related to leases under ASC 842 for the sublease was as follows:

(in thousands)		Three Months Ended March 31, 2021
Operating cash flows from operating leases		$	197

The weighted-average remaining lease term and discount rate for the sublease were as follows:

(in thousands)	As of March 31, 2021
Weighted-average remaining lease term - operating leases	0.8 years
Weighted-average discount rate - operating leases		3.25	%

Future minimum lease payments under non-cancelable operating leases under ASC 842 for the sublease consisted of the following as of March 31, 2021:

Year Ending December 31,	(in thousands)
2021 (remaining 9 months)	$	603
Total future minimum lease payments		603
Less: imputed interest		(7	)
Present value of lease liabilities	$	596

Not included in the table above are the lease payments owing under the Lease the Company entered into in December 2020, pursuant to which the Company has agreed to lease approximately 68,187 square feet of additional office and laboratory space located in Waltham, Massachusetts. The Lease was executed, but not yet commenced as of March 31, 2021. The total expected commitment for this lease will be $40.9 million.

Future minimum lease payments under non-cancelable operating leases under ASC 840 for the sublease and Lease consisted of the following as of December 31, 2020:

Year Ending December 31,	(in thousands)
2021	$	800
2022		4,603
2023		4,741
2024		4,883
2025		5,029
Thereafter		21,672
Total	$	41,728

Summary of Significant Accounting Policies (Policies)

3 Months Ended

Mar. 31, 2021

Accounting Policies [Abstract]

Marketable Securities

Marketable securities

Property and Equipment

Property and equipment

		Estimated Useful Life
Laboratory equipment		5 years
Furniture and fixtures		5 years
Computer equipment		3 years
Leasehold improvements		Shorter of life of lease or 10 years

Leases

Segment Information

Segment information

Fair Value Measurements

Fair value measurements

•	Level 1—Unadjusted quoted prices in active markets that are accessible to the reporting entity at the measurement date for identical assets and liabilities.

•	Level 2—Inputs other than quoted prices in active markets for identical assets and liabilities that are observable either directly or indirectly for substantially the full term of the asset or liability. Level 2 inputs include the following:

•

quoted prices for similar assets and liabilities in active markets;

•

quoted prices for identical or similar assets or liabilities in markets that are not active;

•

observable inputs other than quoted prices that are used in the valuation of the asset or liabilities (e.g., interest rate and yield curve quotes at commonly quoted intervals); and

•

inputs that are derived principally from or corroborated by observable market data by correlation or other means.

•	Level 3—Unobservable inputs for the assets or liability (i.e., supported by little or no market activity). Level 3 inputs include management’s own assumptions about the assumptions that market participants would use in pricing the asset or liability (including assumptions about risk).

Net Loss Per Share

Net loss per share

Cash and Cash Equivalents

Cash includes cash in readily available checking accounts and cash equivalents include all highly liquid investments maturing within 90 days from the date of purchase.

Restricted Cash

Amounts included in restricted cash represent amounts pledged as collateral for letters of credit required for security deposits on the Company’s leased facilities. Restricted cash totaled $2.7 million and $2.3 million at March 31, 2021 and December 31, 2020, respectively. These amounts are classified as a component of other current assets and as restricted cash on the Company’s condensed consolidated balance sheets.

- Definition

Disclosure of accounting policy for segment reporting.

+ References + Details

Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2021

Fair Value Disclosures [Abstract]

Summary of Marketable Securities by Security Type

The following tables set forth by security type, marketable securities for the periods presented:

	As of March 31, 2021
(in thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses			Total
Commercial paper	$	20,882	$	4	$	—		$	20,886
Certificates of deposit		119,450		3		(78	)		119,375
Corporate debt securities		11,957		1		—			11,958
US treasury notes		19,915		2		—			19,917
Total	$	172,204	$	10	$	(78	)	$	172,136

	As of December 31, 2020
(in thousands)	Amortized Cost		Unrealized Gains		Unrealized Losses			Total
Commercial paper	$	6,412	$	—	$	—		$	6,412
Certificates of deposit		1,504		—		—			1,504
Corporate debt securities		36,573		—		(27	)		36,546
Total	$	44,489	$	—	$	(27	)	$	44,462

Summary of Assets Carried at Fair Value on Recurring Basis

The following tables set forth by level, within the fair value hierarchy, the assets carried at fair value on a recurring basis for the periods presented:

	Fair value measurements as of March 31, 2021
(in thousands)	Level 1		Level 2		Level 3		Total
Assets:
Cash equivalents
Money market funds	$	185,544	$	-	$	-	$	185,544
Commercial paper		4,250		—		—		4,250
Marketable securities
Commercial paper		20,886		—		—		20,886
Certificates of deposit		—		11,958		—		11,958
Corporate debt securities		—		119,375		—		119,375
US treasury notes		19,917		—		—		19,917
Total	$	230,597	$	131,333	$	—	$	361,930

	Fair Value Measurements as of December 31, 2020
(in thousands)	Level 1		Level 2		Level 3		Total
Assets:
Cash equivalents
Money market funds	$	155,017	$	—	$	—	$	155,017
Commercial paper		2,999		—		—		2,999
Certificates of deposit		—		5,309		—		5,309
Marketable securities
Commercial paper		6,412		—		—		6,412
Certificates of deposit		—		1,504		—		1,504
Corporate debt securities		—		36,545		—		36,545
Total	$	164,428	$	43,358	$	—	$	207,786

Summary of Scheduled Maturity for Marketable Securities

The following table summarizes the scheduled maturity for the Company’s marketable securities at March 31, 2021:

(in thousands)	March 31, 2021
Maturing in one year or less	$	119,510
Maturing in one year through two years		52,626
Maturing after two years		—
Total	$	172,136

Stock-Based Awards (Tables)

3 Months Ended

Mar. 31, 2021

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Assumptions Used to Determine Grant-Date Fair Value of Options Granted

The assumptions that the Company used to determine the grant-date fair value of options granted were as follows:

	Three Months Ended March 31,
	2021		2020
Expected volatility	74%		75%
Risk-free interest rate	0.88% — 1.13%		0.79% — 1.67%
Expected term (in years)		6		6
Expected dividend yield		—		—

Summary of Stock Option Activity and Related Information

A summary of the Company’s stock option activity and related information for the three months ended March 31, 2021 is as follows:

(in thousands, except share and per share data)	Options			Weighted Average Exercise Price		Weighted Average Remaining Life (in years)		Aggregate Intrinsic Value
Outstanding as of January 1, 2021		6,421,589		$	6.97		9.5	$	90,112
Granted		361,000			17.70
Exercised		(11,163	)		1.20
Canceled		—			—
Outstanding as of March 31, 2021		6,771,426		$	7.55		9.3	$	59,244
Options exercisable as of March 31, 2021		822,408		$	5.34		9.0	$	8,810
Options vested or expected to vest as of March 31, 2021		6,771,426		$	7.55		9.3	$	59,244

Summary of RSU Activity

A summary of the Company’s RSU activity and related information for the 2020 Plan for the three months ended March 31, 2021:

	Number of Shares Underlying RSUs		Weighted Average Grant Date Fair Value
Issued and unvested as of January 1, 2021		403,355	$	23.60
Granted		85,900		17.67
Vested		—
Forfeited		—
Issued and unvested as of March 31, 2021		489,255	$	22.62

Summary of Restricted Common Stock Award Activity

The following table summarizes the Company’s restricted common stock award activity for the three months ended March 31, 2021:

	Number of Restricted Shares
Issued and unvested as of January 1, 2021		370,329
Vested		(70,539	)
Issued and unvested as of March 31, 2021		299,790

Summary of Stock-based Compensation Expense

The Company recorded stock-based compensation expense in the following expense categories of its statements of operations:

	Three Months Ended March 31,
(in thousands)	2021		2020
Research and development	$	1,571	$	25
General and administrative		2,081		41
Total	$	3,652	$	66

Net Loss Per Share (Tables)

3 Months Ended

Mar. 31, 2021

Earnings Per Share [Abstract]

Schedule of Earnings Per Share, Basic and Diluted

Basic and diluted net loss per share was calculated as follows:

	Three Months Ended March 31,
(in thousands, except share and per share data)	2021			2020
Numerator:
Net loss	$	(24,968	)	$	(7,886	)
Denominator:
Weighted-average common shares outstanding used in net loss per share—basic and diluted		49,472,497			8,756,513
Net loss per share—basic and diluted	$	(0.50	)	$	(0.90	)

Potential Dilutive Securities Excluded From Calculation Of Net Loss Per Share

	March 31,
	2021		2020
Options to purchase common stock		6,771,426		1,498,222
Unvested restricted common stock		299,790		581,944
Unvested restricted stock units		489,255		—
Convertible preferred stock (as converted to common stock)		—		10,401,270
Total		7,560,471		12,481,436

Commitments and Contingencies (Tables)

3 Months Ended

Mar. 31, 2021

Commitments And Contingencies Disclosure [Abstract]

Components of Lease Cost for the Sublease

The components of lease cost under ASC 842 for the sublease were as follows:

(in thousands)	Three Months Ended March 31, 2021
Operating lease cost	$	190
Short term lease cost		—
Variable lease cost		114
Total lease cost	$	304

Supplemental Disclosure of Cash Flow Information Related to Leases for the Sublease

Supplemental disclosure of cash flow information related to leases under ASC 842 for the sublease was as follows:

(in thousands)		Three Months Ended March 31, 2021
Operating cash flows from operating leases		$	197

Schedule of Weighted Average Remaining Lease Term and Discount Rate for the Sublease

The weighted-average remaining lease term and discount rate for the sublease were as follows:

(in thousands)	As of March 31, 2021
Weighted-average remaining lease term - operating leases	0.8 years
Weighted-average discount rate - operating leases		3.25	%

Schedule of Future Minimum Lease Payments under Non-Cancelable Operating Leases for the Sublease

Future minimum lease payments under non-cancelable operating leases under ASC 842 for the sublease consisted of the following as of March 31, 2021:

Year Ending December 31,	(in thousands)
2021 (remaining 9 months)	$	603
Total future minimum lease payments		603
Less: imputed interest		(7	)
Present value of lease liabilities	$	596

Future minimum lease payments under non-cancelable operating leases under ASC 840 for the sublease and Lease consisted of the following as of December 31, 2020:

Year Ending December 31,	(in thousands)
2021	$	800
2022		4,603
2023		4,741
2024		4,883
2025		5,029
Thereafter		21,672
Total	$	41,728

Stock-Based Awards - Additional Information (Details) $ / shares in Units, $ in Millions		3 Months Ended
	Sep. 16, 2020 shares	Mar. 31, 2021 USD ($) Installment $ / shares shares	Mar. 31, 2020 $ / shares	Jan. 01, 2021 shares	Sep. 15, 2020 shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average grant date fair value of options granted \| $ / shares		$ 11.44	$ 0.68
Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation expense \| $		$ 21.8
Unrecognized share based compensation expense, recognition period		2 years 7 months 6 days
Unrecognized compensation cost related to unvested stock-based awards with performance-based vesting conditions for which performance conditions not deemed probable \| $		$ 2.6
Restricted Stock Units ("RSUs")
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation expense \| $		$ 8.3
Unrecognized share based compensation expense, recognition period		2 years 9 months 18 days
Number of share of common stock receivable upon vesting		1
2020 ESPP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total number of shares of common stock authorized	488,414
Number of shares available for future issuance	488,414
Percentage of outstanding shares increased annually under the plan	1.00%
Increase in common stock reserved for future issuance	1,953,656
2018 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total number of shares of common stock authorized					8,267,252
Number of shares available for future issuance					1,928,487
2020 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares available for future issuance		5,062,689
Number of shares initially reserved for issuance	4,884,233			2,272,345
Percentage of outstanding shares increased annually under the plan	5.00%
2020 Plan \| Restricted Stock Units ("RSUs")
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights		The Company grants RSUs with service conditions that vest in four equal annual installments provided that the employee remains employed with the Company. The Company also grants RSUs with performance-based vesting conditions for which performance was not deemed probable at March 31, 2021
Share-based Compensation Arrangement By Share-based Payment Award Grant Service Conditions to Vest Number of Annual Installments \| Installment		4

Stock-Based Awards - Summary of Stock Option Activity and Related Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Options
Outstanding, beginning of period	6,421,589
Granted	361,000
Exercised	(11,163)
Outstanding, end of period	6,771,426	6,421,589
Options exercisable as of March 31, 2021	822,408
Options vested or expected to vest as of March 31, 2021	6,771,426
Weighted Average Exercise Price
Outstanding, beginning of period	$ 6.97
Granted	17.70
Exercised	1.20
Outstanding, end of period	7.55	$ 6.97
Options exercisable as of March 31, 2021	5.34
Options vested or expected to vest as of March 31, 2021	$ 7.55
Weighted Average Remaining Life (in years)
Outstanding	9 years 3 months 18 days	9 years 6 months
Options exercisable as of March 31, 2021	9 years
Options vested or expected to vest as of March 31, 2021	9 years 3 months 18 days
Aggregate Intrinsic Value
Outstanding	$ 59,244	$ 90,112
Options exercisable as of March 31, 2021	8,810
Options vested or expected to vest as of March 31, 2021	$ 59,244

Net Loss Per Share - Calculation of Basic and Diluted Net Loss per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Numerator:
Net loss	$ (24,968)	$ (7,886)
Denominator:
Weighted-average common shares outstanding used in net loss per share—basic and diluted	49,472,497	8,756,513
Net loss per share—basic and diluted	$ (0.50)	$ (0.90)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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Reference 19: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g)(1)(ii))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 60B
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121326447&loc=SL5780133-109256

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8933-108599

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22658-107794

+ Details

Commitments and Contingencies - Additional Information (Details) $ in Millions	1 Months Ended	3 Months Ended
	Dec. 31, 2020 USD ($) ft²	Mar. 31, 2021 USD ($) ft²	Mar. 31, 2020 USD ($)
Leases [Abstract]
Lease executed date		Jul. 01, 2019
Lease expiration date		Dec. 31, 2021
Additional leased office space \| ft²	68,187
Lease term	8 years 7 months
Lease, description		The Company’s obligation for the payment of base rent for the Premises begins seven months after the commencement date and will be $0.4 million per month, increasing up to $0.5 million during the term of the Lease. The Company has two options to extend the term of the Lease, each for a period of an additional five years. The term of this lease will commence on the earlier of the date the Company commences its business operations on the Premises or the date the agreed upon improvements to the Premises are substantially completed and necessary occupancy permits are obtained. The Company expects the Premises to be ready for occupancy in the second half of 2021.
Monthly rent expense	$ 0.4
Increase in monthly rent expense	$ 0.5
Lessee operating lease existence of option to extend	true	true
Option to extend lease		The Company has two options to extend the term of the Lease, each for a period of an additional five years
Additional period of lease	5 years
Rent expense		$ 0.2	$ 0.2
Additional office and laboratory space \| ft²		68,187
Total expected commitment for lease		$ 40.9

Commitments and Contingencies - Schedule of Future Minimum Lease Payments under Non-Cancelable Operating Leases for the Sublease (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Operating Lease Liabilities Payments Due [Abstract]
2021 (remaining 9 months)	$ 603
Total future minimum lease payments	603
Less: imputed interest	(7)
Present value of lease liabilities	$ 596
2021		$ 800
2022		4,603
2023		4,741
2024		4,883
2025		5,029
Thereafter		21,672
Total		$ 41,728

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Mar. 31, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001
Preferred stock, shares authorized	10,000,000
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	51,458,066	45,446,903
Common stock, shares outstanding	51,158,276	45,076,574

Condensed Consolidated Statements of Stockholders' Equity (Deficit) (Unaudited) (Parenthetical) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Common Stock
Stock issuance costs	$ 0.7
Series A Redeemable Convertible Preferred Stock
Stock issuance costs		$ 0.1

Nature of the Business and Basis of Presentation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions			3 Months Ended
	Jan. 25, 2021	Sep. 21, 2020	Mar. 31, 2021
Nature Of Business And Basis Of Presentation [Line Items]
Entity incorporation date			Dec. 01, 2017
Initial Public Offering \| Common Stock
Nature Of Business And Basis Of Presentation [Line Items]
Number of shares issued and sold		14,089,314
Underwriters option to purchase additional shares		1,837,736
Public offering price		$ 19.00
Net proceeds from issuance of common stock		$ 246.4
Follow-on Public Offering \| Common Stock
Nature Of Business And Basis Of Presentation [Line Items]
Number of shares issued and sold	6,000,000
Public offering price	$ 28.00
Net proceeds from issuance of common stock	$ 157.2

Summary of Significant Accounting Policies - Schedule of Estimated Useful Lives of Property, Plant and Equipment (Details)	3 Months Ended
	Mar. 31, 2021
Laboratory Equipment
Property Plant And Equipment [Line Items]
Property, plant and equipment, useful life	5 years
Furnitures and Fixtures
Property Plant And Equipment [Line Items]
Property, plant and equipment, useful life	5 years
Computer Equipment
Property Plant And Equipment [Line Items]
Property, plant and equipment, useful life	3 years
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property, plant and equipment, useful life	Shorter of life of lease or 10 years

Summary of Significant Accounting Policies - Additional Information (Details) $ in Millions	1 Months Ended	3 Months Ended
	Dec. 31, 2020	Mar. 31, 2021 Segment	Jan. 01, 2021 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Lease term, description		The Company classifies leases with a term greater than one year as either operating or finance leases at the lease commencement date and records a right-of-use assets and current and non-current lease liabilities, as applicable on the balance sheet.
Lessee operating lease existence of option to extend	true	true
Number of operating segment \| Segment		1
Minimum
Summary Of Significant Accounting Policies [Line Items]
Lease term		1 year
Maximum
Summary Of Significant Accounting Policies [Line Items]
Lease term not to recognize on balance sheet		1 year
Accounting Standards Update 2016-02
Summary Of Significant Accounting Policies [Line Items]
Lease liabilities			$ 0.8
Right-of-use assets			$ 0.7

Cash, Cash Equivalents and Restricted Cash - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents [Abstract]
Cash and cash equivalent maturity period	90 days
Restricted cash	$ 2.7	$ 2.3

Fair Value Measurements - Summary of Marketable Securities by Security Type (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 172,204	$ 44,489
Unrealized Gains	10
Unrealized Losses	(78)	(27)
Total	172,136	44,462
Commercial Paper
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	20,882	6,412
Unrealized Gains	4
Total	20,886	6,412
Certificates of Deposit
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	119,450	1,504
Unrealized Gains	3
Unrealized Losses	(78)
Total	119,375	1,504
Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	11,957	36,573
Unrealized Gains	1
Unrealized Losses		(27)
Total	11,958	$ 36,546
US Treasury Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	19,915
Unrealized Gains	2
Total	$ 19,917

Fair Value Measurements - Summary of Assets Carried at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Assets:
Total	$ 361,930
Fair Value, Recurring
Assets:
Total		$ 207,786
Level 1
Assets:
Total	230,597
Level 1 \| Fair Value, Recurring
Assets:
Total		164,428
Level 2
Assets:
Total	131,333
Level 2 \| Fair Value, Recurring
Assets:
Total		43,358
Cash Equivalents \| Money Market Funds
Assets:
Total	185,544
Cash Equivalents \| Money Market Funds \| Fair Value, Recurring
Assets:
Total		155,017
Cash Equivalents \| Commercial Paper
Assets:
Total	4,250
Cash Equivalents \| Commercial Paper \| Fair Value, Recurring
Assets:
Total		2,999
Cash Equivalents \| Certificates of Deposit \| Fair Value, Recurring
Assets:
Total		5,309
Cash Equivalents \| Level 1 \| Money Market Funds
Assets:
Total	185,544
Cash Equivalents \| Level 1 \| Money Market Funds \| Fair Value, Recurring
Assets:
Total		155,017
Cash Equivalents \| Level 1 \| Commercial Paper
Assets:
Total	4,250
Cash Equivalents \| Level 1 \| Commercial Paper \| Fair Value, Recurring
Assets:
Total		2,999
Cash Equivalents \| Level 2 \| Certificates of Deposit \| Fair Value, Recurring
Assets:
Total		5,309
Marketable Securities \| Corporate Debt Securities
Assets:
Total	119,375
Marketable Securities \| Corporate Debt Securities \| Fair Value, Recurring
Assets:
Total		36,545
Marketable Securities \| Commercial Paper
Assets:
Total	20,886
Marketable Securities \| Commercial Paper \| Fair Value, Recurring
Assets:
Total		6,412
Marketable Securities \| Certificates of Deposit
Assets:
Total	11,958
Marketable Securities \| Certificates of Deposit \| Fair Value, Recurring
Assets:
Total		1,504
Marketable Securities \| US Treasury Securities
Assets:
Total	19,917
Marketable Securities \| Level 1 \| Commercial Paper
Assets:
Total	20,886
Marketable Securities \| Level 1 \| Commercial Paper \| Fair Value, Recurring
Assets:
Total		6,412
Marketable Securities \| Level 1 \| US Treasury Securities
Assets:
Total	19,917
Marketable Securities \| Level 2 \| Corporate Debt Securities
Assets:
Total	119,375
Marketable Securities \| Level 2 \| Corporate Debt Securities \| Fair Value, Recurring
Assets:
Total		36,545
Marketable Securities \| Level 2 \| Certificates of Deposit
Assets:
Total	$ 11,958
Marketable Securities \| Level 2 \| Certificates of Deposit \| Fair Value, Recurring
Assets:
Total		$ 1,504

Fair Value Measurements - Additional Information (Details) - USD ($)	Mar. 31, 2021	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Fair value assets, transfers among level 1, level 2 or level 3	$ 0	$ 0

Fair Value Measurements - Summary of Scheduled Maturity for Marketable Securities (Details) $ in Thousands	Mar. 31, 2021 USD ($)
Marketable Securities And Fair Value Measurements [Abstract]
Maturing in one year or less	$ 119,510
Maturing in one year through two years	52,626
Total	$ 172,136

Property and Equipment - Schedule of Property and Equipment (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Property Plant And Equipment [Line Items]
Property and equipment—at cost	$ 3,010	$ 2,941
Less accumulated depreciation and amortization	(1,233)	(995)
Property and equipment—net	1,777	1,946
Laboratory Equipment
Property Plant And Equipment [Line Items]
Property and equipment—at cost	2,763	2,744
Office and Computer Equipment
Property Plant And Equipment [Line Items]
Property and equipment—at cost	79	78
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment—at cost	14	14
Construction in Process
Property Plant And Equipment [Line Items]
Property and equipment—at cost	$ 154	$ 105

Property and Equipment - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Property Plant And Equipment [Abstract]
Depreciation and amortization expense	$ 238	$ 150

Accrued Expenses and Other Current Liabilities - Schedule of Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Payables And Accruals [Abstract]
Payroll and benefits	$ 779	$ 2,105
Consulting services	340	263
Legal services	131	325
Research and development	5,844	4,782
Facility costs		52
Total	$ 7,094	$ 7,527

Stock-Based Awards - Summary of RSU Activity (Details) - Restricted Stock Units ("RSUs") - 2020 Plan	3 Months Ended
	Mar. 31, 2021 $ / shares shares
Number of Shares Underlying RSUs
Issued and unvested as of January 1, 2021 \| shares	403,355
Granted \| shares	85,900
Issued and unvested as of March 31, 2021 \| shares	489,255
Weighted Average Grant Date Fair Value
Issued and unvested as of January 1, 2021 \| $ / shares	$ 23.60
Granted \| $ / shares	17.67
Issued and unvested as of March 31, 2021 \| $ / shares	$ 22.62

Stock-Based Awards - Summary of Restricted Common Stock Award Activity (Details) - Restricted Common Stock	3 Months Ended
	Mar. 31, 2021 shares
Number of Restricted Shares
Issued and unvested as of January 1, 2021	370,329
Vested	(70,539)
Issued and unvested as of March 31, 2021	299,790

Stock-Based Awards - Summary of Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 3,652	$ 66
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	1,571	25
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 2,081	$ 41

Net Loss Per Share - Potential Dilutive Securities Excluded From Calculation Of Net Loss Per Share (Details) - shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total	7,560,471	12,481,436
Convertible Preferred Stock (As Converted to Common Stock)
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total		10,401,270
Options to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total	6,771,426	1,498,222
Unvested Restricted Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total	299,790	581,944
Unvested Restricted Stock Units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total	489,255

Commitments and Contingencies - Schedule of Weighted Average Remaining Lease Term and Discount Rate for the Sublease (Details)	Mar. 31, 2021
Leases [Abstract]
Weighted-average remaining lease term - operating leases	9 months 18 days
Weighted-average discount rate - operating leases	3.25%